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[82.53.134.131]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49fdace7941sm63084875e9.2.2026.09.22.06.56.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Sep 2026 06:56:27 -0700 (PDT) Date: Tue, 22 Sep 2026 15:56:19 +0200 From: Stefano Garzarella To: David Carlier Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 1/2] vsock: report pending receive data to io_uring Message-ID: References: <20260920194710.1114748-1-devnexen@gmail.com> <20260920194710.1114748-2-devnexen@gmail.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20260920194710.1114748-2-devnexen@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: BQqoQmm0yP1VQqkwHXJsNFlTWKPQBqbjEuDigi1ShsA_1790085388 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline On Sun, Sep 20, 2026 at 08:47:09PM +0100, David Carlier wrote: >AF_VSOCK stream receives never fill msghdr.msg_inq, so io_uring cannot set >IORING_CQE_F_SOCK_NONEMPTY and retries a multishot receive even after the >queue has been drained. > >Fill the hint at the common receive exit using the transport callback that >SIOCINQ already uses, and report 1 once the connection is finished so the >caller performs the receive which observes EOF, as TCP does after a FIN. > >A vsock loopback ping-pong with io_uring multishot receive drops entries >into __vsock_connectible_recvmsg from 1.97 to 1.00 per delivered message, >and receiver CPU time by about 3% (25 runs of 50000 messages, p=0.006). > >Signed-off-by: David Carlier >--- > net/vmw_vsock/af_vsock.c | 39 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 39 insertions(+) > >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >index f840498b58af..63309708c916 100644 >--- a/net/vmw_vsock/af_vsock.c >+++ b/net/vmw_vsock/af_vsock.c >@@ -2543,6 +2543,38 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg, > return err; > } > >+/* Bytes a following receive can consume, 1 if it would only see EOF, or a >+ * negative value to leave the caller's hint alone. >+ * >+ * Called under the socket lock after a nonnegative stream receive, so a NULL >+ * transport implies SOCK_DONE. >+ */ >+static int vsock_inq_hint(struct sock *sk) can we add "stream" in the name so it's clear that is stream only? (e.g. vsock_stream_inq_hint) >+{ >+ struct vsock_sock *vsk = vsock_sk(sk); >+ s64 data; >+ >+ if ((sk->sk_shutdown & RCV_SHUTDOWN) || >+ (sock_flag(sk, SOCK_DONE) && sk->sk_state != TCP_ESTABLISHED)) >+ return 1; >+ >+ if (!vsk->transport) >+ return 1; Can we squash this in the previous block? >+ >+ data = vsock_stream_has_data(vsk); >+ if (data < 0) >+ return -1; >+ if (data > 0) >+ return (int)min_t(s64, data, INT_MAX); nit: IMO we can remove the int cast. >+ >+ /* Empty but finished: keep the caller reading so it sees EOF. */ >+ if (sock_flag(sk, SOCK_DONE) || >+ (READ_ONCE(vsk->peer_shutdown) & SEND_SHUTDOWN)) >+ return 1; >+ >+ return 0; >+} >+ > int > __vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, > int flags) >@@ -2606,6 +2638,13 @@ __vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, > err = __vsock_seqpacket_recvmsg(sk, msg, len, flags); > > out: >+ if (msg->msg_get_inq && err >= 0 && sk->sk_type == SOCK_STREAM) { Why only STREAM? A comment here and in the commit would be nice. >+ int inq = vsock_inq_hint(sk); >+ >+ if (inq >= 0) Why assigning only >= 0 values? Thanks, Stefano >+ msg->msg_inq = inq; >+ } >+ > release_sock(sk); > return err; > } >-- >2.55.0 >